1. Field of the Invention
The present invention relates to transforming adaptors which are comprised of series and parallel circuits including a plurality of capacitors and a plurality of resistors which perform filter operation functions and a balancing network using wave digital filters which are include the transforming adaptors connected in cascade.
2. Description of the Related Art
It is advantageous to use wave digital filters when realizing balancing networks required in two-wire transmission systems for digital signals. This is because, compared with a general digital filter (represented by a cascade connection of an elementary digital filter section and expressed by a second order z function at the numerator and denominator) the correspondence with the balancing network made by passive elements in the analog domain is good and the requisite amount of memory may be reduced. Further, it is easy to obtain a reflected wave at an input terminal of the circuit, required as the output of the balancing network.
The method of designing a digital type balancing network using a wave digital filter is known. The present invention, however, proposes an improvement of the operating method of construction and an improvement of the characteristics.
As explained in more detail later, a wave digital filter type balancing network has various merits over a general digital filter, but suffers from the problem of a greater amount of filter operations per each basic sampling clock and therefore the size of the hardware becomes larger.